linux-kernel - Re: [PATCH] update sc->nr_reclaimed after each shrink

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Message-ID: <20160722081828.GE794@dhcp22.suse.cz>
Date:	Fri, 22 Jul 2016 10:18:28 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Zhou Chengming <zhouchengming1@...wei.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, riel@...hat.com, guohanjun@...wei.com
Subject: Re: [PATCH] update sc->nr_reclaimed after each shrink_slab

On Fri 22-07-16 11:12:59, Vladimir Davydov wrote:
> On Fri, Jul 22, 2016 at 09:49:13AM +0200, Michal Hocko wrote:
> > On Fri 22-07-16 11:43:30, Zhou Chengming wrote:
> > > In !global_reclaim(sc) case, we should update sc->nr_reclaimed after each
> > > shrink_slab in the loop. Because we need the correct sc->nr_reclaimed
> > > value to see if we can break out.
> > 
> > Does this actually change anything? Maybe I am missing something but
> > try_to_free_mem_cgroup_pages which is the main entry for the memcg
> > reclaim doesn't set reclaim_state. I don't remember why... Vladimir?
> 
> We don't set reclaim_state on memcg reclaim, because there might be a
> lot of unrelated slab objects freed from the interrupt context (e.g.
> RCU freed) while we're doing memcg reclaim. Obviously, we don't want
> them to contribute to nr_reclaimed.
> 
> Link to the thread with the problem discussion:
> 
>   http://marc.info/?l=linux-kernel&m=142132698209680&w=2

Ohh, now I rememeber again. Thanks for the refresh ;)

So the patch doesn't make any difference in the end.
-- 
Michal Hocko
SUSE Labs